[Clang] Fix incorrect return type for __builtin_shufflevector

[jhuber6]

Summary:
The __builtin_shufflevector call would return a GCC vector in all
cases where the vector type was increased. Change this to preserve
whether or not this was an extended vector.

Fixes: #107981

[llvmbot]

@llvm/pr-subscribers-clang

Author: Joseph Huber (jhuber6)

Changes

Summary:
The __builtin_shufflevector call would return a GCC vector in all
cases where the vector type was increased. Change this to preserve
whether or not this was an extended vector.

Fixes: #107981

---

Full diff: https://github.com/llvm/llvm-project/pull/154817.diff

2 Files Affected:

• (modified) clang/lib/Sema/SemaChecking.cpp (+5-2)
• (modified) clang/test/AST/ByteCode/constexpr-vectors.cpp (+6-1)

diff --git a/clang/lib/Sema/SemaChecking.cpp b/clang/lib/Sema/SemaChecking.cpp
index 2944c1a09b32c..c39236cd5f8f8 100644
--- a/clang/lib/Sema/SemaChecking.cpp
+++ b/clang/lib/Sema/SemaChecking.cpp
@@ -5601,8 +5601,11 @@ ExprResult Sema::BuiltinShuffleVector(CallExpr *TheCall) {
                                       TheCall->getArg(1)->getEndLoc()));
     } else if (numElements != numResElements) {
       QualType eltType = LHSType->castAs<VectorType>()->getElementType();
-      resType =
-          Context.getVectorType(eltType, numResElements, VectorKind::Generic);
+      if (resType->isExtVectorType())
+        resType = Context.getExtVectorType(eltType, numResElements);
+      else
+        resType =
+            Context.getVectorType(eltType, numResElements, VectorKind::Generic);
     }
   }
 
diff --git a/clang/test/AST/ByteCode/constexpr-vectors.cpp b/clang/test/AST/ByteCode/constexpr-vectors.cpp
index f19adad3323f2..81ec6aac4bee3 100644
--- a/clang/test/AST/ByteCode/constexpr-vectors.cpp
+++ b/clang/test/AST/ByteCode/constexpr-vectors.cpp
@@ -15,7 +15,6 @@ using FourFloatsExtVec __attribute__((ext_vector_type(4))) = float;
 using FourDoublesExtVec __attribute__((ext_vector_type(4))) = double;
 using FourI128ExtVec __attribute__((ext_vector_type(4))) = __int128;
 
-
 // Next a series of tests to make sure these operations are usable in
 // constexpr functions. Template instantiations don't emit Winvalid-constexpr,
 // so we have to do these as macros.
@@ -875,3 +874,9 @@ void BoolVecUsage() {
   constexpr auto k = ~FourBoolsExtVec{true, false, true, false};
   static_assert(k[0] == false && k[1] == true && k[2] == false && k[3] == true, "");
 }
+
+using EightBoolsExtVec __attribute__((ext_vector_type(8))) = bool;
+void BoolVecShuffle() {
+  constexpr EightBoolsExtVec a = __builtin_shufflevector(
+      FourBoolsExtVec{}, FourBoolsExtVec{}, 0, 1, 2, 3, 4, 5, 6, 7);
+}

[efriedma-quic]

I expect this doesn't have much effect in most cases; we have a bunch of implicit conversions between vector types, so probably in most cases the vector gets converted to the right type before anyone actually tries to use it.

LGTM